S«pt«*lb«('7S 



il 

 Is 

 •I 



Figure 61. Carbon dioxide flux 



measurements in a deltaic salt marsh 

 community (unpublished data; see Gosselink 

 et al. 1977). 



all the production can 

 the grass. 



be attributed to 



Most of the respiration is associated 

 with the diatom and microbial community 

 (aufwuchs) on the base of the plant culms 

 and sediment surface. In Figure 62 I show 

 annual C fluxes calculated from these 

 data, adjusted for the difference in 

 average biomass in the cuvette compared to 

 the surrounding marsh but not corrected 

 for light intensity, marsh flooding, and 

 temperature variation (see Gosselink et 

 al . 1977 for details of the technique). 



Comparable data from other delta salt 

 marsh studies is displayed for comparison 

 in Table 29. Organic matter has been 

 converted to carbon by multiplying by 0.4 

 (Smith et al. 1932a). The differences 

 from earlier budgets are startling. Gross 

 community production was estimated to be 



METHANE 

 (5) 



GROSS 



PRODUCTION 



4680 



SALT MARSH 



LEACHING 

 (140) 



ABOVE GROUND 

 BELOW GROUND 



►(850)-! 



► 2680-' 



3265 



PLANT 



CONSUMERS 



▼ 



SEDIMENTS 



(265) 



EXPORTED 

 AND 

 -► UNEXPLAINED 

 SALT 



1120 



RESPIRATION 

 1010 



RESPIRATION 

 2140 



Figure 62. Carbon budget of a Mississippi River deltaic salt marsh (see Table 29 for 

 sources). Rates (g C/m^/yr) are from CO2 flux measurements, except numbers in 

 parentheses, which are from other sources. 



72 



